Yield and selectivity analysis of a bubble flow using the example of toluene oxidation

• Applicant: Professor Dr.-Ing. Ulrich Nieken
• Subject Area: Chemical and Thermal Process Engineering
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256634524

Yield and selectivity of a bubbly flow are influenced by the kinetic of the reaction network, the mass transport, the macroscopic mixing of a two-phase flow as well as the microscopic mix-ing in the bubble wake. To predict yield and product selectivities in a reactive bubble swarm with reasonable accuracy the rates of the involved mechanisms should be determined from separate, independent studies. The parameter determined by experiments or numerical cal-culations are input to a two-flow model to determine the product formation under the prevailing conditions.Within that context the ICVT is planning the following particular projects.i) The determination of a macroscopic kinetics for a technical synthesis with a radical chain mechanism without influence of a possible mass transport limitationIn the ongoing project phase a kinetic apparatus for measurement under homogeneous con-ditions was set up and successfully operated. The evaluation of the measurement was diffi-cult due to the susceptible analysis. Further improvements are required. The developed ki-netics is to be made available to AK Rzehak and AK Hlawitschka for a later model validation. Once available, a portable Raman probe from the AK Rinke is to be tested for online analysis.ii) Experiments for validation of the calculation methodology for the prediction of yield and selectivity in a bubble flowThe institute has a bubble column available which is to be operated at elevated pressure and temperatures. After an adaptation of the periphery, the reactive [Fe2(HPTB)Cl3]-model sys-tem of the AK Schindler is to be measured, followed by the toluene oxidation. The measure-ments are used to validate the calculation methodology in AK Rhezak and AK Hlawitschka.iii) Studies on the influence of the mixture on the bubble scale on the product selectiv-itiesThe influence of the mixing processes on the bubble scale can only be considered in macro-scopic simulations in the form of correlations to the "corrections" of the kinetics. In order to assess the influence on product selectivity, a simplified model is to be developed. The aim is to investigate the conditions under which these are necessary and, as the case may be, to develop a simplified calculation methodology which allows the effects of the mixture on the bubble scale to be integrated into the macroscopic calculation. We are cooperating here with the AK Marschall to compare simplified and detailed simulations. Furthermore, an intensive exchange concerning the methodology with the AK Hampel / Kryk has been agreed to.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1740: The Influence of Local Transport Processes on Chemical Reactions in Bubble Flows
• Co-Investigator: Dr.-Ing. Ute Susanne Tuttlies